(1) Field of the Invention
The present invention relates to the handling of sheet material and particularly to the delivery of a continuous web of material provided with register marks to a work station continuously and in synchronism with the operation of the work station apparatus. More specifically, this invention is directed to apparatus for feeding a web of material provided with register marks and especially to apparatus for adjusting the speed of delivery to a work station of an indicia bearing continuous ribbon such that it will be received at the work station with the indicia properly positioned for operation of the work station apparatus. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well-suited for use in effecting the delivery of a paper web having a pattern repetitively printed thereon to a work station such as, for example, a cutter which severs the web into individual sheets which are subsequently used for packaging or the like. In such case, the printed matter should preferably be situated as centrally as possible on each of the sheets into which the web is divided. The feeding and cutting operation are, of course, preferably performed continuously and at a high working speed.
As is well-known, it is virtually impossible to continuously feed a web of material, particularly a printed paper web, in such a manner as to avoid some offset, for example slippage, between the feed apparatus and the web. Any such offset will result in a loss of synchronism and, in the case where a repetitive printed pattern is being divided into individual portions, the printed matter will thus not be maintained in the desired position on the individual cut sheets. Accordingly, apparatus for effecting feed correction is necessary. Prior art methods of and apparatus for achieving such feed correction are described in Federal Republic of Germany Published Patent Applications Ser. Nos. 1,461,932 and 2,338,109 and in East German Patent Specification No. 148,043.
The apparatus and techniques of the above-mentioned publications are exemplary of the prior art technique of employing a sensor, a photocell for example, which responds to register marks on the web of moving material. In the prior art the difference in time between the detection of a register mark by the sensor and predetermined timing intervals are measured. A speed adjusting device responsive to deviations in the measured time from a desired value was employed to adjust feed speed so as to remove the offset thereby accomplishing the requisite synchronized feed. The apparatus of the prior art is characterized by comparatively complex circuitry which, due to its complexity, is expensive and of somewhat suspect reliability.